While the bolt pattern is the same 6x5.5 as the older trucks, the wheelbackspacing and offset are different. Wheels from an '88-'98 4x4 or a '99-current 1/2 ton will not directly bolt up to the '70 and older 2wd and '87 and older 4x4 without hitting the control arms and tie rods. Some sort of adapter would be required.
Since you're talking about 20" or 22' wheels, you will need to take into consideration a few more things, namely BRAKES, clearance, and tire load capacity. Note I capitalized brakes. By going with a large wheel like that, the brakes will need to be upgraded, preferably 4 wheel disk with power assist, with a 12" minimum rotor diameter. This is due to the extra weight the large wheels add over the stock wheels. Clearance could be an issue, depending on how wide you go with the tire. You may have to either increase the ride hight, or trim the fenders for clearance to allow for turning the front wheels. On the tires, lower aspect ratios generally lead to lower load capacity, as well as higher running pressures to maintain the rated capacity. This, in addition to the increased unsprung weight, will lead to poor ride quality. The larger tires, especially the wide versons, are also very sensative to alignment and rotation, and they tend to wear quickly.
